Why did He say "Nidrashti l'Lo Sha'alu"?
Rashi: Hashem answers him, it is impossible not to take vengeance against them, for I made Myself available to those who seek Me, rebuke them via My Nevi'im, and they did not ask.
Radak: Hashem answers Bnei Galus - exile has lasted so long because your fathers' sins were great; they served idolatry and transgressed the Mitzvos. I was prepared for them to seek Me; they did not ask.
Malbim: It is as if the Navi awakens, and says with Ru'ach ha'Kodesh, why do you complain about Me? You say that I held back and hid My eye. I sought you via the Nevi'im, but you did not ask the Navi!
Why does it add "Nimtzeisi l'Lo Vikshuni"?
Radak: The matter is repeated four times, to strengthen it. It says also "Amarti... [Lo Kora vi'Shmi]; Perasti" (2). He sent many times via the Nevi'im, e.g. "Shuvu Elai v'Ashuvah Aleichem" (Mal'achi 3:7).
Malbim: I am available to fulfill their request, but they did not request from Me.
Why did He say "Hineni Hineni"?
Rashi: Repent to Me, and I am ready to receive.
Malbim: It is as if I am prepared for all that they will command, and they will not need to request and seek Me.
What is "Goy Lo Kora vi'Shmi"?
Rashi: The nation did not want to be called on My name.
Radak: (a) It is as if Yisrael is not called on My name, Am Hashem (Malbim - Am Elokei Yisrael). (b) They did not turn to Me.